For us, the most interesting part of iTunes 8 is the Genius feature. Not because it's essentially a new way of selling you stuff from the iTunes Store. But because if you have a massive library of music, it seems to be a fun way of rediscovering music you already have, even if it is pretty similar to what Last.fm has been doing for ages.

One way we've achieved this before is by using the Smart Playlist feature of iTunes. It's easy to tell iTunes to create a playlist of, say, 25 rock songs that you've heard at least five times (so you must at least enjoy each track), but that haven't been played for at least two months. Click OK and boom -- automatic playlist created.

Genius takes this one step further in a different direction, adds automation, and allows you to create these custom playlists on the new iPods. And in our tests it appeared to work fairly well -- you select a track you like, click the Genius button, and you're given a playlist of songs similar to your source track.

We started off our test with Adenosine Buildup by Blotted Science -- an extremely complex experimental metal song, full of changing time signatures, unpredictable tempo changes and an erratic song structure. The Genius playlist generated from this included songs from Dream Theater, The Dillinger Escape Plan, Necrophagist and Meshuggah -- all metal bands with songs containing fast, extremely technical songwriting, frantic time-signature changes and unusual composition.

Next we chose as our source track a song by Japanese pop artist Ai Otsuka. Not only did Genius build a playlist of similar songs, but it also pulled in other Japanese pop songs from the likes of Bonnie Pink, Do As Infinity, Tokyo Jihen and Hitomi Yaida.

A playlist based on a Will Smith track contained Black Eyed Peas, 50 Cent and The Streets; based on punk band NOFX we got a playlist of punk from The Offspring, Blink 182 and The Distillers, among others; and based on Puncture Wound Massacre by Cannibal Corpse we got 25 songs from the likes of Decapitated, Deicide, The Black Dahlia Murder and Nile.

All very impressive. But Genius isn't idiot-proof, and we did manage to break it...